|Publication number||US4631958 A|
|Application number||US 06/591,180|
|Publication date||Dec 30, 1986|
|Filing date||Mar 19, 1984|
|Priority date||Apr 15, 1983|
|Also published as||CA1200114A, CA1200114A1|
|Publication number||06591180, 591180, US 4631958 A, US 4631958A, US-A-4631958, US4631958 A, US4631958A|
|Inventors||Roger Van Cauwenberghe, Jiri Motycka|
|Original Assignee||Canadian Patents And Development Limited|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (3), Non-Patent Citations (2), Referenced by (14), Classifications (6), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This invention relates to an apparatus for measurement of velocity of fluids, in particular to the measurement of wind speed. The invention has particular usefulness in the determination of two orthogonal components of the mean velocity of wind in limits between 5 cm/sec and 50 m/sec.
Techniques involving the use of a drag sphere have previously been employed for measurement both in air and water. However, these systems proved to be insufficiently sensitive in the low range of wind velocities where the dynamic force is relatively low due to the square root relation between the wind force and the wind velocity.
Furthermore, the instruments were not usable in the wide range of environmental conditions encountered in meteorological stations. Furthermore, these instruments were not easily de-iceable.
It is an object of this invention to provide an improved, more sensitive sensor for the measurement of two orthogonal wind speeds or of wind speed and its direction.
A further object of this invention is to provide a sensor with a small surface exposed to ice deposition capable of being de-iced with a low power expense.
It is a still further object of this invention to provide a drag sphere sensor with an output proportional more closely to wind speed rather than to the wind force.
It is a still further object of this invention to provide a force-balance anemometer utilizing a null principle in which the wind force is opposed by a internally generated force of electromagnetic actuator, so that the measuring shaft will be motionless, no elastic element will be employed as in many other force-measuring devices and hysteresis or temperature offset would tend not to originate from such an elastic element.
It is a still further object of this invention to provide an anemometer with its output available in an electronic form to be transmitted through standard communication channels, or if desired, recorded, displayed or interfaced with a computer.
It is a still further object of this invention to provide an anemometer substantially free of hysteresis and internal friction with a suitable damping usable also in liquids, such as water, by filling the internal volume of the instrument and the neck around the shaft protruding out of the instrument body with a liquid such as silicone oil. The liquid in the neck forms an interface seal due to surface tension preventing water or other undesirable matter from entering the instrument body. Small amounts of the filing fluid that are lost on the interface are, according to the present invention, replenished at the rate of several droplets a day by an oil supply system.
It is a still further object of this invention to provide a compensator of thermal expansion of the liquid located inside the instrument. The compensator is a block of a plastic material which expands with the temperature increase and forms more space inside the instrument for the liquid to expand. The level of liquid in the neck of the instrument body is, therefore, constant and does not fluctuate with ambient temperature changes. The instrument can also be used without the oil supply system and the compensator of its thermal expansion.
Other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment of the invention which is illustrated in the accompany drawings.
FIG. 1 is a diagrammatic side elevational view of one embodiment of the invention;
FIG. 2 is a diagrammatic view of an oil supply system;
FIG. 3 is a perspective view of the oil volume compensator;
FIG. 4 is a diagrammatic side elevational view of another embodiment of of the invention;
FIG. 5 is an exploded view of the means for suspending the shaft of the anemometer; and
FIG. 6 is a sectional side elevational view of a portion of the shaft and suspension means.
Referring to FIG. 1, the anemometer forming the preferred embodiment of the invention has a drag sphere 1 attached to a shaft 2 mounted into the center of an elastic element 3. The elastic element 3 has a shape of a cruciform or a diaphragm supported by the outer edges on the body of the instrument 3a.
A rectangular ferrite block 4 is attached to the lower end of the shaft 2. A four coil system 5 is arranged around the ferrite block 4 to form the electromagnetic actuator, which generates a force proportional to the square of the current flowing through the coil. Only one of each two opposing coils 5 is energized at a time. The coils can be wound on E-cores as shown or on other shapes, such as C-cores.
A rectangular shield 6 is a basic part of the optical sensing means for detecting angular deflection of the shaft 2. The edges of the shield are illuminated by light transmitted through four fiber optic bundles 8 from a single light emitting diode 9. Four photoelectric detectors 7 are located on the opposite side of the shield 6. Each two opposing detectors 7 are connected in an antiparallel manner to provide a signal proportional to the deflection of the shaft from its neutral position. The signal is amplified and brought into the proportional and integral control of the actuator 5 in a sense acting to decrease the shaft deflection back to zero. As a result, the actuator keeps the shaft in its central position, generates a force balancing the wind force in two orthogonal directions, and provides two outputs--proportional to the actuator currents--that are a measure of two orthogonal wind speeds. To eliminate the influence of instrument tilt and linear acceleration, the unit is mechanically balanced. In the free-hand shaft position, the optical position detector must be well centered to provide a zero signal (without electrical offset). This eliminates the error signal due to temperature changes.
The oil level will move up and down as a result of the thermal expansion of the oil. This could change the shaft balance if the instrument were tilted. To minimize this effect, the volume of oil is kept small by potting the coils in an epoxy filler. Also, the annulus between the shafts 2 and oil supply is large to prevent surface tension of the oil from causing moments at the oil/air interface.
Mechanical temperature effects have been minimized by the use of the same material for the cruciform 3 and its support. Optical thermal effects are also minimized by the use of photodiode detectors 7 produced from the same wafer and by their illumination by a single LED 9.
Additional features of the anemometer include a body filled with a liquid such as silicone oil, forming a level in a neck around the shaft at 11, electronics 10, oil supply unit 12 and oil volume compensator 17.
As shown in FIG. 2, the oil supply system includes a body 12, a piston 13, a spring 14, the oil reserve 15 and one or more small passages 16 leading from the oil supply 15 into the internal cavity of the instrument.
As shown in FIG. 3, an oil volume compensator 17 includes a body 17a having several cavities 18 enclosed by lids 19. Inside each cavity 18 there is a metal block filling most of the space. The cavities 18 are mutually interconnected by passages 20 and the entire compensator can be connected to the instrument internal cavity by connector 21. The function of the compensator is as follows:
The volume of oil in the instrument changes with temperature and, therefore, the oil level in the neck around the shaft would fluctuate. When the oil level is low, there would be a possibility of water getting into the instrument and when the level is high there would be losses of oil flowing out of the neck. In order to keep the level constant, the oil volume changes are exactly matched by volume changes of cavities 18 in plastic body 17. The volume of each of the cavities 18 in the plastic body 17 is chosen in such a way that thermal volume changes are equal to those of the oil in the instrument. To make the compensator more efficient and keep the total volume of oil in the instrument and in the compensator as low as possible, the compensator cavities 18 are filled with metal cylinders.
Referring to FIG. 4, showing another embodiment of the invention without the oil supply and temperature compensation system, the anemometer has a de-icing heater not shown located on a body neck protruding inside the drag element 1. The heater is energized by icing sensors 22.
The cruciform 3, shown in FIGS. 5 and 6, is chemically milled from 0.12 mm thick spring steel. This method provides both excellent strength in the vertical and horizontal directions, as well as good sensitivity to the angular shaft motion caused by elastic strain in arms 40. An outer ring 42 prevents an arm from shifting in its mount and thus avoids any buckling of the cruciform 3. Four short arms 46 at 45° allow its attachment as by screws 47 to shaft flanges 48 to prevent any rotation about the vertical axis. The shaft flanges clamp the cruciform 3 just at the center, leaving the entire length of the four arms 40 free for angular motion. The vertical motion of the shaft is limited by a set of stops. Identical rings 50, having recesses 52, are provided above and below the cruciform 3 so as to clamp the outer edge of the cruciform 3. The shaft flanges 48 are received in the recesses 52. The bottom ring 50 is fastened to the instrument body 3a. It will be noted that clearance is provided at 56 to function as a motion stop to prevent overload of the cruciform 3 in a vertical direction.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US3077783 *||Mar 24, 1959||Feb 19, 1963||Gen Precision Inc||Two-axis accelerometer|
|GB1408139A *||Title not available|
|GB2052047A *||Title not available|
|1||Dessuveault et al., "The Design of a Thrust Anemometer for Drifting Buoy", Ocean 81 Conference Record (IEEE), Sep. 1981, pp. 411-414.|
|2||*||Dessuveault et al., The Design of a Thrust Anemometer for Drifting Buoy , Ocean 81 Conference Record (IEEE), Sep. 1981, pp. 411 414.|
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|US5231876 *||May 17, 1991||Aug 3, 1993||Peet Bros. Company, Inc.||Method and apparatus for wind speed and direction measurement|
|US5361633 *||May 10, 1993||Nov 8, 1994||Peet Bros. Company, Inc.||Method and apparatus for wind speed and direction measurement|
|US6279393||Aug 24, 1999||Aug 28, 2001||Mountain High E&S||System for isotropically measuring fluid movement in three-dimensions|
|US6402816||Apr 7, 2000||Jun 11, 2002||Gordon S. Trivett||Gas scrubber|
|US7117735||Jun 29, 2004||Oct 10, 2006||Kevin Owen Shoemaker||Fluid flow direction and velocity sensor|
|US7742153||Oct 1, 2007||Jun 22, 2010||University Of Utah Research Foundation||Miniature opto-mechanical anemometer|
|US20050022592 *||Jun 29, 2004||Feb 3, 2005||Shoemaker Kevin Owen||Fluid flow direction and velocity sensor|
|US20080088819 *||Oct 1, 2007||Apr 17, 2008||Meredith Metzger||Miniature opto-mechanical anemometer|
|CN102455367B *||Oct 15, 2010||Dec 24, 2014||捷和电机（深圳）有限公司||风速计|
|WO2003031989A1 *||Oct 9, 2002||Apr 17, 2003||Ramaioli Francesco||Single sensor to measure the wind speed and the wind direction without parts in movement|
|WO2003067265A1 *||Dec 9, 2002||Aug 14, 2003||Kollstad Tor Einar||Flow measuring device and method|
|WO2012048660A1 *||Oct 14, 2011||Apr 19, 2012||Chiaphua Components (Shenzhen) Limited||Anemometer|
|U.S. Classification||73/170.16, 73/862.61, 73/170.15|
|Feb 3, 1986||AS||Assignment|
Owner name: CANADIAN PATENTS AND DEVELOPMENT LIMITED-SOCIETE C
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:CAUWENBERGHE, ROGER VAN;MOTYCKA, JIRI;REEL/FRAME:004505/0740;SIGNING DATES FROM
|Jul 31, 1990||REMI||Maintenance fee reminder mailed|
|Dec 30, 1990||LAPS||Lapse for failure to pay maintenance fees|
|Mar 12, 1991||FP||Expired due to failure to pay maintenance fee|
Effective date: 19901230